This application relates to a method for reversibly filtering radiant energy and radiant energy absorption means therefor. More particularly, the present invention involves an efficient, easily reversible electrolytic process for regulating the transmission of radiant energy requiring a low electrical potential. The present invention also relates to a radiant energy filter adapted for use with the above-identified transmission regulation process. As used in the present application, the term "radiant energy" refers not only to the visible portion of the radiant energy spectrum but also to other forms of radiation, such as infra-red and ultra-violet.
To date, the methods and devices for regulating the transmission of radiant energy have involved, usually, mechanical or electro-mechanical devices. Typical examples of such devices are the shutters used on the normal building window or on a camera, as well as the filters which can be mounted over the window or over the camera lens. However, such prior art devices have a number of disadvantages. A basic disadvantage is that all such mechanical and electro-mechanical shutters and filters are external to the optical structure (i.e., the window or camera lens) and thus decrease the esthetic appeal of the optical part. Also, such structures are subject to mechanical positioning problems with respect to the optical part. Furthermore, shutters customarily restrict the field of vision of the optical system while the usual filter is not capable of adjustment with respect to the amount of radiant energy transmitted.